Like a non-sequitur, a pre-sequitur doesn't follow what immediately preceded it, but instead relates to something that came much earlier. It is a sudden or jarring break in the chronology, but it does follow... when you remember what it refers to.

Jen: Why did you leave Los Angeles?
Keith: Well... have you ever lived there?
Jen: I visited once, for a week. I liked the street performers on the boardwalk...
Keith: Oh, the boardwalk is where I got this red scarf!
Jen: I was trying to knit a scarf just like that last year but I never finished.
Keith: Where do you get yarn around here?
Jen: There's a good store just a few blocks from here, wanna come see?

... ten minutes later ...

Jen: Huh, do you smell Indian food?
Keith: Hmm, not really... but now I'm in the mood to get some Indian Food.
Jen: Sure, let's!
Keith: It was the pollution, that's why.
Jen: pollution?
Keith: Yeah, I wanted somewhere with real air, and LA wasn't it!
Jen: Oh, why you left Los Angeles

Like a non-sequitur, a pre-sequitur doesn't follow what immediately preceded it, but instead relates to something that came earlier, but too long ago to be relevant. It is a sudden or jarring break in the chronology, but it does follow... when you remember what it refers to. Often used as a comic device.

A classic pre-sequitur:
during Mary's job interviewLou Grant: What religion are you?
Mary Richards: Mr. Grant, I don't quite know how to say this, but you're not allowed to ask that when someone's applying for a job. It's against the law.
Lou Grant: Wanna call a cop?
Mary Richards: No.
Lou Grant: Good. Would you think I was violating your civil rights if I asked if you're married?
Mary Richards: Presbyterian.

actually there is no such thing as a presequitur, but there is a common misconcepton that there is something of that nature which exists. The Phallacy results due to an ignorance of linguistic derivation commonly known as ontology.
Non means "without"
sequitur means following
therefore non sequitur means without following
in some examples people mistakenly believe a presequitur is something that crops up from a previous conversation in a new conversation - but this is still merely a non sequitur

a) Dude are you sure about this presequitur business
b) oh absolutely certain - doesnt exist
a) fried eggs ?
b) hmmm what?
a) thats what i think we ate that on tabletop mountain
b) ahaha oh I get it you used a non-sequitur
a) yes to illustrate the point that its not a pre-sequitur